A wide variety of organic phosphate and thiophosphate esters are known to be useful as insecticides and acaricides. In such compounds, the phosphate or thiophosphate residue may be attached to a heterocyclic nucleus. For example, the United States Patent No. 2,754,244, granted July 10th 1956 to Hans Gysin et al, discloses pyrazolyl phosphoric and thiophosphoric acid esters which are stated to have good insecticidal and acaricidal activity. However, it has been found that the utility of such esters varies widely with the nature of the organic radicals that they contain, and that even small changes in chemical structure can give rise to substantial differences in insecticidal and acaricidal activity. Substantial research has therefore been directed towards finding compounds of this general type having the most desirable combination of properties, particularly high and wide-ranging insecticidal and acaricidal activity combined with relatively low toxicity to warm-blooded animals and a persistence suited to the end use envisaged. The present invention provides new thiophosphoric acid esters in which the thiophosphoric ester residue is attached to a pyrazoline nucleus.
The pyrazoline derivatives of the present invention are the .DELTA..sup.2 -pyrazoline compounds of the general formula:- ##SPC2##
Wherein Ar represents a phenyl radical optionally substituted by one, two or three atoms or radicals, which may be the same or different, selected from halogen (preferably chlorine) atoms, alkyl and alkoxy radicals each containing 1 to 4 carbon atoms, the trifluoromethyl radical and the nitro radical, and R.sub.1 and R.sub.2 are the same or different and each represents a hydrogen atom or the methyl radical.
According to a feature of the invention, these pyrazoline derivatives are prepared by the process which comprises reacting 0,0-diethylchlorothiophosphate with a pyrazolidinone of the general formula: ##SPC3## which, in an alkaline medium, reacts in the tautomeric enol form: ##SPC4##
The symbols Ar, R.sub.1 and R.sub.2 being as hereinbefore defined. An alkali metal derivative of a compound of general formula III, optionally prepared in situ, is generally used.
The reaction is preferably carried out in an organic solvent such as 2-N-methylpyrrolidone, dimethylformamide, hexamethylphosphotriamide or dimethylsulphoxide, at a temperature between 0.degree. and 30.degree.C.
The pyrazolidinone derivatives of general formula II can be prepared by reacting a .beta.-halogenated acid halide of the general formula: ##EQU1## wherein Y represents a halogen atom, e.g. chlorine, bromine or iodine, and Z represents a halogen (preferably chlorine) atom, with a hydrazine of the general formula: EQU Ar -- NH -- NH.sub.2 V
wherein Ar is as hereinbefore defined.
The pyrazoline derivatives of general formula I possess useful insecticidal and acaricidal properties. They are particularly active through contact and by direct ingestion, especially against diptera, coleoptera, lepidoptera, hemiptera and orthoptera. They are also excellent soil insecticides.
The pyrazoline derivatives also possess useful nematicidal activity. They have proved particularly active in vivo against Ditylenchus dipsaci and Meloidogyne incognita at rates of application of between 1 and 100 kg. per hectare and are preferably used in the treatment of soil in the form of dusts.
According to a further feature of the present invention, there are provided insecticidal, acaricidal and nematicidal compositions containing, as the active ingredient, at least one pyrazoline derivative of formula I in association with one or more diluents or adjuvants compatible with the pyrazoline derivative(s) and suitable for use in agricultural insecticidal, acaricidal and nematicidal compositions. Preferably the compositions contain between 0.005 and 80% by weight of pyrazoline derivative.
The compositions may be solid if there is employed a powdered solid compatible diluent such as talc, calcined magnesia, kieselguhr, tricalcium phosphate, powdered cork, adsorbent charcoal, or a clay such as kaolin or bentonite. These solid compositions are preferably prepared by grinding the pyrazoline derivative with the solid diluent, or by impregnating the solid diluent with a solution of the pyrazoline derivative in a volatile solvent, evaporating the solvent, and if necessary grinding the product so as to obtain a powder.
Instead of a solid diluent, there may be used a liquid in which the pyrazoline derivative is dissolved or dispersed. The compositions may thus take the form of suspensions, emulsions or solutions in organic or aqueous-organic media, for example acetophenone, aromatic hydrocarbons such as toluene or xylene or mineral, animal or vegetable oils, or mixtures of these diluents. The compositions in the form of suspensions, emulsions or solutions may contain wetting, dispersing or emulsifying agents of the ionic or non-ionic type, for example sulphoricinoleates, quaternary ammonium derivatives or products based on condensates of ethylene oxide, such as the condensates of ethylene oxide with octylphenol, or fatty acid esters of anhydrosorbitols which have been rendered soluble by etherification of the free hydroxyl groups by condensation with ethylene oxide. It is preferable to use agents of the non-ionic type because they are not sensitive to electrolytes. When emulsions are required, the pyrazoline derivatives may be used in the form of self-emulsifying concentrates containing the active substance dissolved in the emulsifying agent or in a solvent containing an emulsifying agent compatible with the pyrazoline derivative and solvent, a simple addition of water to such concentrates producing compositions ready for use.
The pyrazoline derivatives of general formula I are preferably employed in a quantity of 10 to 100 g. per hectoliter of water when they are used for spraying at a rate of approximately 1 hectoliter per hectare.
In the treatment of soil, the best results are obtained by using the pyrazoline derivatives at a rate of 1 to 100 kg. of active material per hectare.
The pyrazoline derivatives of general formula I wherein Ar represents a phenyl radical substituted by one, two or three atoms or radicals selected from chlorine and the nitro radical, the phenyl radical carrying at most one nitro radical, and R.sub.1 and R.sub.2 are the same or different and each represents a hydrogen atom or the methyl radical, are of outstanding interest.
The following compounds are especially active as insecticides and acaricides:
1-(2,4-dichlorophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline, 1-(4-chlorophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline, 1-(2,4,5-trichlorophenyl)-3-0,0-diethylthionophosphoryl-.DELT A..sup.2 -pyrazoline, 1-(3,5-dichlorophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline, 1-(3-chlorophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline, 1-(4-nitrophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline and 1-(2-chloro-4-nitrophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline.
The following compounds are especially active as nematicides:
1-(3,5-dichlorophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline, 1-(3-chlorophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline, 1-(2-chlorophenyl)-3-0,0-diethylthionophosphoryl-4,4-dimethyl -.DELTA..sup.2 -pyrazoline, 1-(4-nitrophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline and 1-(2-chloro-4-nitrophenyl)-3-0,0-diethylthionophosphoryl-.DELTA..sup.2 -pyrazoline.
The following Examples illustrate the preparation of pyrazoline derivatives of the present invention.